Sciatica refers to pain that radiates along the path of the sciatic nerve, which branches from your lower back through your hips and buttocks and down each leg. Typically, sciatica affects only oneside of your body. It’s often caused by a herniated disc, bone spur on the spine, or narrowing of the spine (spinal stenosis) that compresses part of the nerve. This can result in inflammation, pain, and often some numbness in the affected leg.